fix: check for None explicitly to prevent incorrect behaviour when answer is 0

Author: marcelblijleven

src/adventofcode/util/helpers.py

@@ -44,7 +44,7 @@ def wrapper(*args, **kwargs):
                 start = time.perf_counter()
                 solution = func(*args, **kwargs)
 
-                if not solution:
+                if solution is None:
                     raise SolutionNotFoundException(year, day, part)
 
                 diff = time.perf_counter() - start